<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
</head>
<style>
  .container{
    display: flex;
  }
  .left{
    width: 200px;
    height: 200px;
    background: saddlebrown;
  }
  .right {
    width: 200px;
    height: 200px;
    background: rebeccapurple;
  }
  .center{
    flex: 1;
    height: 200px;
    background: rosybrown;
  }
</style>
<body>
  <div class="container">
    <div class="left">左边</div>
    <div class="center">zhongian</div>
    <div class="right">右边</div>
  </div>
</body>
</html>